JPS6145549A - Charged particle ray device - Google Patents

Abstract

PURPOSE:To make it possible to correct with high accuracy a relatively positional relation of a sample to the charged electron rays in order to minimize divergence of a visual field due to inclination or rotation of a sample by digital performance of detection and correction of positional divergence. CONSTITUTION:When finished to scan one line, a deflection control unit 11 controls unit 11 controls a deflection signal generator 2 so as to perform line scanning in the Y-axis direction 1 while the coordinates of the edge part of a sample image are held by each register X and Y. Thereafter, when a sample fine-moving stand 16 is inclined, the coordinates of the edge part of the sample image are held by DELTAX or DELTAY registers. In this way, when a difference in the contents of X and DELTAX register or Y and DELTAY register, which are held, is generated and positional divergence is detected, its difference is taken out by the subtractors 17 and 18 for being converted into analogue value by the digital-analogue converters and being outputted to a deflector 3 with the direction and sensitivity where the positional difference may be minimized. As its result, the position of the electron beam 4 on the sample is shifted thus, as a result, generating no divergence of a visual field.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to charged particle beam devices such as scanning electron microscopes and similar devices. The present invention relates to a new device that can maintain a constant value.

[Background of the invention]

Condition 1 desired for a sample fine movement device is ideally for the sample to rotate or tilt at the center of the field of view, but this is mechanically difficult to achieve. Previously, JP-A-51-11756
As described in Publication No. 9, one position shift can be detected and corrected in an analog manner, for example, by detecting the phase difference between the images before and after tilting the sample, and converting the phase difference into a voltage to determine the position of the charged particle beam. However, there was a limit to the ability to accurately correct misalignment.

[Purpose of the invention]

An object of the present invention is to detect a shift in the field of view position due to the tilt or rotation of the sample, and to correct the relative positional relationship between the sample and the valence electron beam with high precision so that this shift is minimized. An object of the present invention is to provide a charged particle beam device.

[Summary of the invention and examples]

In order to achieve the above objective, it is first necessary to carefully examine the specimen image and decide where in it to be fixed.

A scanning electron microscope (hereinafter referred to as a scanning electron microscope) is an example of a sample observation device.
SEM), whose operation is well known and will not be described in detail, will be explained below by taking the SEM as an example.

FIG. 1 shows an example of a SEM image. That is, C
It is assumed that the RT screen A can be viewed, for example, by synchronously scanning the sample two-dimensionally with an electronic beam. Therefore, in this case, limited scanning (see FIG. 2) is required to cover the sample image (3). As a result, the target sample A', image 1 has been extracted, so this sample image ■3 can be stored as is, but as expected, when the sample is tilted, the resulting sample Since the images become different, it becomes difficult to detect the desired positional deviation.

In order to eliminate this drawback, in the present invention, the detection target is a portion (edge portion) where the brightness of the sample image changes when at least one or more lines are scanned. For example, as shown in FIG. 3, when a line scan indicated by X is performed in the axial direction, the resulting video signal is output as a waveform d. Compare this waveform d at the slice level.

When binarized, waveform F is obtained.6 Then, for example, if the time tX until the rise of waveform F is determined, the distance Qx from the scanning start point can be determined as QX=□・tx (μm). (Here, - is the scanning speed of the beam.) In other words, sample mechanics.

The coordinate in the X direction is determined.

Next, switch the scanning to the direction indicated by yl, and do the same with 1y.
seek. By these operations, the coordinates of sample image (3) are detected.

After detecting the coordinates as described above, 1. For example, if the sample is slightly tilted, 13
Assume that the position has shifted with respect to . Here, as mentioned above, if the electronic bee 11 is scanned in the line indicated by X in the X-axis direction as shown in FIG. The amount of deviation X11 from the coordinates before tilting the sample is ΔXn=K (t
x txn). I want to, ΔXn
All you have to do is move the sample fine movement stage in the direction and amount that minimizes it. However, in practice (
There may be cases where the desired accuracy cannot be obtained due to play in the t"ja 4'J section. In such a case, the same result can be obtained even if the electron beam is shifted to the X axis.

Specifically, a DC bias having a deflection sensitivity corresponding to ΔX may be supplied to the electron beam X-ray deflector.

After completing the following operations, the same procedure is performed in the Y-axis direction. Once the positional deviation has been corrected in the Y-axis direction, the sample is tilted slightly in the desired direction again, and the same process is repeated until the sample is tilted to the desired tilt. Nevertheless, the sample mechanism does not escape from the field of view, which means that the object of the present invention, which is to tilt the sample at the center of the field of view, has been achieved.

At first glance, the operations detailed above may seem troublesome in PHAt, but they are performed automatically and it takes only a short time to complete the series of operations. For example, assuming that the desired amount of positional deviation due to one tilt for coordinate position detection is 0.5 μm, and assuming that the total amount of deviation when tilting to the desired inclination is 1000 μm, the current maximum scanning of the SEM An example of speed is 1m s/1
The approximate time required to complete the line is approximately 4 seconds.

Hereinafter, an embodiment in which the present invention is applied to a SEM will be described with reference to FIG. In the figure, block 1 shows one embodiment of the present invention.

First, the output of the deflection signal generator 2 drives the deflector 3, so that the electron beam 1% 4 scans and deflects the sample 5 while irradiating it. As a result, the secondary electron signal 6 generated from the sample 5 is detected by the detector 7 and transmitted to the CR via the amplifier 8.
This becomes a T9 brightness modulation signal. On the other hand, the deflection signal generator 2
Since λJ outputs a deflection signal to the deflector jO of the CRT 9, an image of the sample 5 is displayed on the CRT 9. For example, a result like the example shown in FIG. 1 can be obtained.

Next, when the deflection control section 11 controls the LM width and DC level of the deflection signal generator 2, for example, FIG. 2 is realized.

After the above two operations, when the deflection control unit 11 is set to the sample fixing mote, the deflection signal generator 2 is set so that the deflection control unit 11 performs line scanning alternately in the X direction and the Y direction at a period of about 1 ms.
control. First, when the first scan in the X direction is started, the counter 13 is reset at this timing.
At the same time, the oscillator 12 is activated and generates a clock with a period of approximately 17zs, which is counted by the counter 13. When the scanning progresses and a sample image signal is generated at the output of the amplifier 8 as shown in waveform d in FIG. 3, the signal is binarized by the binarization circuit 14,
Waveform F appears on output line 15. A part of the output line 15 is X
is added to the register, and the contents of counter 13 at this time are
held in a register. Furthermore, the output line 15 also has the function of stopping the oscillation of the oscillator 12.

When one line of line scanning is completed through the above operations, the deflection control unit 11 controls the deflection signal generator 2 to perform one line scanning in the Y-axis direction. The effect of this result is exactly the same as for the X-axis. however.

The contents of counter 13 are held in the Y register.

These operations are performed for about 2 ms.

Through the above operations, the coordinates of the edge portion of the sample machine shown in FIG. 3, for example, are held in each of the X and Y registers. Thereafter, when the sample fine movement stage 16 is tilted manually or by using a motor or the like, the coordinate data of the edge portion of the sample image is held in the ΔX or ΔY register through the same process as described above. (The contents of the X and Y registers are not changed.

On the other hand, the contents of the ΔX and ΔY registers are updated every time line scanning in the same direction is performed. ) In this way, when a difference occurs between the contents of the held X and ΔX registers or Y and ΔY register, that is, when a positional shift is detected, the difference is written to the reducer 17 and 18 and taken out. Re,
Followed by a 9.20 analog converter. As a result, the position of the electron beam 4 on the sample shifts, and as a result, the field of view position does not shift.
It becomes two.

〔Effect of the invention〕

As described in detail below, according to the present invention, since positional deviation is detected and corrected digitally, the relative positional relationship between the sample and the charged particle beam can always be kept accurately and constant. can. As a result, compared to the conventional analog method of calculating the phase difference and correcting two positions, if applied to a sample fine movement mechanism with a rotation mechanism, the height at the center of the field of view can be reduced. 2. If you want to keep the charged particle beam at the same point for a long time, for example, if you apply it to an XMA device, sample drift and electron beam drift can be corrected with high precision. , the accuracy of analysis is improved.

Japanese 1. The present invention has been described with respect to a charged particle beam device having scanning and deflection functions, but in the case of a transmission electron microscope, for example, it can be implemented by photographing a stationary sample image with a television camera or the like. .

[Brief explanation of the drawing]

Figure 1 shows an example of a SEM image, Figure 2 shows a sample image taken on a CRT (131 m) when the field of view is restricted, and Figure 3
The figure shows an example of the sample image signal waveform as a result of line scanning, Figure 4 is a diagram explaining that the field of view position shifts when the sample is tilted, and Figure 5 is a diagram when the present invention is implemented in an SEM. It is a figure showing one example of this. DESCRIPTION OF SYMBOLS 1... Entire block diagram of the present invention, 2... Deflection signal generator, 3, 10... Deflector, 4...'' Koko beat t1
．． 5... Sample, 6... Secondary electron, 7... Detector,
8... Φ amplifier, 9... CRT, 11... Deflection control section, 12... Oscillator,... 13... Counter,
14... Binarization circuit, 16... Sample fine movement table, 17.
18...l compensator, 19.20...digital-to-analog converter. ldo-1- Representative Patent Attorney Katsuo Ogawa, 3.゛. ■Wow JJlo Figure 2■. Work 2 %3 Figure 1 P5

Claims (1)

[Claims] 1. means for irradiating a sample with a charged particle beam, means for deflecting the particle beam on the sample, means for detecting a sample information signal as a result of the irradiation, display means for displaying an image based on the information signal, and In a charged particle beam device consisting of the above-mentioned sample micro-motion device, a portion of the sample image displayed as an image that includes at least a portion where a change in brightness has occurred is selected, and scanning up to the selected portion is performed. A means for detecting and holding the amount of movement of the charged particle beam from the starting point, and a means for detecting the amount of movement from the starting point of the scan to the above part after the holding, and a difference with respect to the held movement amount. What is claimed is: 1. A charged particle beam apparatus comprising: means for determining the difference; and means for correcting the relative positional relationship between the charged particle beam and the sample in accordance with the difference.